Arsenal await scan results on Francis Coquelin’s injury on Monday amid fears he could be ruled out for the rest of the season with sprained knee ligaments, Football Insider sources understand.

Coquelin was assessed by the club’s medical team on Sunday and a senior Gunners source has told Football Insider that their diagnosis is that the Frenchman has sprained the medial collateral ligament in his knee.

The midfielder, who limped off 14 minutes into the team’s 2-1 defeat at West Brom on Saturday, has been told by medics to brace himself for a lengthy absence.

Arsenal are awaiting the results of scans later on Monday before they can determine the precise extent of the injury but they fear Coquelin will be sidelined for between three and six months.

The worst-case scenario is that the Frenchman will not be able to return until the end of May, ruling him out of playing again for Arsene Wenger’s title challengers this season.

Coquelin’s expected lengthy absence is a shattering blow for Arsenal as they attempt to maintain their Premier League title challenge and avoid elimination from the Champions League group stages.

The 24-year-old has been a bedrock of Wenger’s team in 2015, with his central midfield alliance with Santi Cazorla key to their improved form.

Coquelin has now joined Arsenal’s mounting casualty list, which already includes Aaron Ramsey, Alex Oxlade-Chamerlai, Theo Walcott and long-term absentees Danny Welbeck, Jack Wilshere and Tomas Rosicky. Mikel Arteta, who was Coquelin’s replacement at the Hawthorns, also suffered a calf injury on Saturday and was substituted 35 minutes after coming on.

Wenger might be forced to rush one or both of Oxlade-Chamberlain and Ramsey back into action after absences of four and six matches respectively.

Under pressure: Arsene Wenger will face calls to sign a midfielder in January

Wenger will speak to the media about his fellow Frenchman’s injury at Monday lunchtime ahead of Tuesday night’s must-win Champions League clash against Dynamo Zagreb at Emirates Stadium.

The Londoners must defeat their Croatian visitors to avoid elimination from the group stages of Europe’s most high-profile club competition.

Wenger will now face further pressure to strengthen his already struggling squad in the forthcoming January transfer window to keep Arsenal’s title bid on track.